11,465 research outputs found
Deformed Carroll particle from 2+1 gravity
We consider a point particle coupled to 2+1 gravity, with de Sitter gauge
group SO(3,1). We observe that there are two contraction limits of the gauge
group: one resulting in the Poincare group, and the second with the gauge group
having the form AN(2) \ltimes \an(2)^*. The former case was thoroughly
discussed in the literature, while the latter leads to the deformed particle
action with de Sitter momentum space, like in the case of kappa-Poincare
particle. However, the construction forces the mass shell constraint to have
the form p_0^2 = m^2, so that the effective particle action describes the
deformed Carroll particle.Comment: 10 page
State morphism MV-algebras
We present a complete characterization of subdirectly irreducible MV-algebras
with internal states (SMV-algebras). This allows us to classify subdirectly
irreducible state morphism MV-algebras (SMMV-algebras) and describe single
generators of the variety of SMMV-algebras, and show that we have a continuum
of varieties of SMMV-algebras
Coherent states for the q-deformed quantum mechanics on a circle
The q-deformed coherent states for a quantum particle on a circle are
introduced and their properties investigated.Comment: 11 pages, 2 PostScript figure
Tsallis' deformation parameter q quantifies the classical-quantum transition
We investigate the classical limit of a type of semiclassical evolution, the
pertinent system representing the interaction between matter and a given field.
On using as a quantifier of the ensuing dynamics Tsallis q-entropy, we
encounter that it not only appropriately describes the quantum-classical
transition, but that the associated deformation-parameter q itself
characterizes the different regimes involved in the process, detecting the most
salient fine details of the changeover.Comment: 19 pages, 7 figure
Discrete Accidental Symmetry for a Particle in a Constant Magnetic Field on a Torus
A classical particle in a constant magnetic field undergoes cyclotron motion
on a circular orbit. At the quantum level, the fact that all classical orbits
are closed gives rise to degeneracies in the spectrum. It is well-known that
the spectrum of a charged particle in a constant magnetic field consists of
infinitely degenerate Landau levels. Just as for the and
potentials, one thus expects some hidden accidental symmetry, in this case with
infinite-dimensional representations. Indeed, the position of the center of the
cyclotron circle plays the role of a Runge-Lenz vector. After identifying the
corresponding accidental symmetry algebra, we re-analyze the system in a finite
periodic volume. Interestingly, similar to the quantum mechanical breaking of
CP invariance due to the -vacuum angle in non-Abelian gauge theories,
quantum effects due to two self-adjoint extension parameters and
explicitly break the continuous translation invariance of the
classical theory. This reduces the symmetry to a discrete magnetic translation
group and leads to finite degeneracy. Similar to a particle moving on a cone, a
particle in a constant magnetic field shows a very peculiar realization of
accidental symmetry in quantum mechanics.Comment: 25 pages, 2 figure
A Guide to the Cost of Progesterone for Prevention of Preterm Labor
Progesterone, in various forms, has been the sole pharmacologic weapon against preterm labor supported by randomized controlled trials since the early 2000s. Nightly vaginal suppositories and weekly injections were the first forms of progesterone proved to be effective in preventing preterm labor. The effectiveness of nightly vaginal gel was then demonstrated. These options are all relatively affordable. Suppositories and gel are only available in branded forms and until recently the intramuscular injection form was only available from compounding pharmacies. Several factors must be considered when choosing a product for a patient. These include route of administration, patient preference, local availability and cost
On the definition of velocity in doubly special relativity theories
We discuss the definition of particle velocity in doubly relativity theories.
The general formula relating velocity and four-momentum of particle is given.Comment: 7 page
Health Reform, Health Insurance, and Selection: Estimating Selection into Health Insurance Using the Massachusetts Health Reform
We implement an empirical test for selection into health insurance using changes in coverage induced by the introduction of mandated health insurance in Massachusetts. Our test examines changes in the cost of the newly insured relative to those who were insured prior to the reform. We find that counties with larger increases in insurance coverage over the reform period face the smallest increase in average hospital costs for the insured population, consistent with adverse selection into insurance before the reform. Additional results, incorporating cross-state variation and data on health measures, provide further evidence for adverse selection.
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